Block copolymers are useful as pigment dispersants, surfactants, compatibilizers for polymer blends, thermoplastic elastomers and in a variety of other applications. Polymers with narrow molecular weight dispersity can enhance melt viscosity behavior, solids-viscosity relationships of polymer solutions and sharper melt transitions than the same composition at a higher polydispersity.
Conventional commercial techniques for synthesizing narrow polydispersed polymers and block copolymers include free-radical polymerization. Radical polymerization may be accomplished: (1) through the use of pseudo or quasi-living polymerization. These techniques make use of low molecular weight transfer agents and/or chain terminators; (2) through the use of transformation chemistry; (3) through the use of multifunctional or polymeric initiators.
This invention provides a method of employing certain vinyl compounds in the synthesis of polymers with narrow molecular weight distribution and block copolymers by free radical polymerization Block copolymerization by radical polymerization has been described in PCT Application No WO 93/2355. This PCT application describes the mechanism of block copolymer formation but does not define conditions necessary for the preparation of high purity block copolymers, nor formation of narrow polydispersity resins.